Particle Hair Not Assuming Emitter Color
Having other maps such as normal map will cause all hair to show as black, I duplicate the material and disconnect every texture input other than base color, then assign it as the active material in the particle system to fix this.
I had a similar issue pop up which is unrelated. The hairs had desynchronized from the source mesh and were projecting the UV map in a really bad way. It was using the texture area for the characters mouth and tongue along a good stretch of the back, freaky!
If this happens, Click 'Disconnect Hair' near the top of the particle system setting panel, then after it has changed to 'Connect Hair' click the button again.
Another issue I've had is displaced or outright exploding hair caused by changes to the source mesh, this includes many modifiers and subdivision. Checking 'Use Modifier Stack' did not work for me here, strangely.